Island Rule (ERS winds)

Note: in the course of this work two aspects of the ACOM3 runs were found that affect the results: The MOM model has "partial bottom cells", which make the grid nonhomogeneous, and also has a 50m-thick bottom boundary layer. Taking those thicknesses properly into account is essential to getting the top-to-bottom transport right. See Figs 4.5 for some details. Many plots on this page include streamfunctions or other transport measures from ACOM3. Not all of them have been redone to correct the vertical integrals. To check, look for the notation "PC/BBL" in the lower left corner of each plot (or in the main title).

This will make it tricky to compare ACOM3 and Sverdrup pressures. Choosing a deeper reference level has the problem of topography, which is starting to intrude even at 1000m: ACOM3 bathymetry in the SW Pacific

Divergences: Subdomain regionSE AustraliaThese divergences were found by (1) vertically integrating (u,v), including the partial bottom cells and BBL; (2) interpolating these transports onto a doubled grid; (3) taking centered differences; (4) subsampling to eta grid (centered between (u,v) cells). The values are very high! (1.e-6 m/s = 31.6 m/year)Test streamfunction plots not blanking land: Entire regionDetail 1Detail 2These are all the same streamfunction, but zooming in on the east coast of Australia (Note the effect of the non-zero divergence along 50°S causing some of the vertical stripes. Others are due to divergence along the Australian coast)

Line plots. These are a scattered selection of profiles showing w and the running downward integral of (u_x+v_y)dz. A restriction here is that only profiles where the derivatives could be calculated over 2 gridboxes in each direction all the way to the bottom were used (i.e. where the bottom is flat). Where there is a bottom slope all three scripts lose values at the bottom. Stuart's and Russ's script makes no allowance for the partial bottom cells or BBL. Billy's script "correctly" finds the divergence from these (but the values are plotted here at the standard levels).
Note that at most of these locations, there is a large divergence signal in the partial bottom cell layer (with corresponding w signal). Also note that the contribution of BBL divergence (cyan line and dot at bottom of heavy blue line) is very close to what is needed to bring w (heavy black line) to zero at the bottom, showing that the BBL is essential to getting the divergence right.
The value of each line at the bottom of the profile measures the total divergence at each point (should be zero). Note the different (automatic) scale in each plot.123E,42S123E,49S127E,45S127E,47S155E,37.2S155E,36.8S155E,30S158E,39S158E,37S158E,36S159E,36S159E,35S160E,42S162E,30S166E,5S171E,5SDifferences: w - divergence for the above arbitrary selection of pointsMap showing the above arbitrary selection of points